Gas mixing control method and apparatus



g- 1952 E. x. SCHMlDT ET AL 2,608,199

GAS MIXING CONTROL METHOD AND APPARATUS Filed March 6, 1946 3Sheets-Sheet 1 A g 1952 E. x. SCHMIDT ET AL 2,608,199

GAS MIXING CONTROL METHOD AND APPARATUS Filed March 6, 1946 3Sheets-Sheet 2 26, 1952 E. x. SCHMIDT ET AL ,60 9

GAS MIXING CONTROL METHOD AND APPARATUS Filed March 6, 1946 3Sheets-Sheet 5 I54 I55 I 6 I37 700 E oso-- 3 PEAK SHAVING GAS 6mm U k E600. MINIMUM HEATING VALUE. Q Q 550-- 8 MJ W I I I l 30 4o a0 I00 PEAKSHAVING GAS IN MIXTURE- Patented Aug. 26, 1952 GAS MIXING CONTROL METHODAND APPARATUS Edwin X. Schmidt and Charles W. Warner, Milwaukee, Wis.,assignors to Cutler-Hammer, Inc., Milwaukee, Wis., a. corporation ofDelaware Application March 6, 1946, Serial No. 652,431

8 Claims.

This invention relates to improvements in gas mixing control methods andapparatus, and although not limited thereto the invention relates moreparticularly to such methods and apparatus adapted for peak shaving.

In the operation of gas utilities it frequently becomes necessary ordesirable to supplement the normal maximum supply of gas by an auxiliarysupply consisting of a mixture with air of a liquid petroleum gas orgases. However, a mixture of such gases (propane and/or butane) with airwhich will function satisfactorily on gas burning appliances when usedalone or as a relatively large percentage of the gas flow, invariablyrequires a heating value thereof which is substantially higher than thatof the base gas. The result is that more potential heat is delivered tothe domestic consumer per unit of volume, and the income of the gascompany is reduced due to the lower volumetric consumption. Thereforewhen the demand for gas requires the use of a supplementary fuel, orpeak shaving gas, it is desirable that such additional gas be suppliedat the minimum heating value which will not cause trouble on consumerappliances. Moreover, inasmuch as the proportionality of the peakshaving gas in the mixture determines the amount of increase in heatingvalue required to eliminate burner trouble, the volume of peak shavinggas must be properly proportioned with respect to the volumetric rate offlow of the base gas, and the heating value of the peak shaving gasshould have a definite relationship to the preselected proportionality.

Assuming that a utility normally supplies carbureted water gas of 540 B.t. u. per cubic foot, 2. propane-air mixture of 720 B. t. u. wouldtheoretically be required to provide for substitution thereof completelyfor the carbureted water gas (100 per cent interchangeability). However,we have found that a 700 B. t. u. mixture of propane and air will affordsatisfactory burner performance. Similarly, we have found that a mixtureof carbureted water gas of the aforementioned quality with up to aboutper cent of 540 B. t. u. propane-air (peak shaving) gas will likewiseafford satisfactory burner performance. On the other hand, if one-halfof the final mixture consists of carbureted water gas of theaforementioned quality and the balance a propane airgas mixture, aheating value of the latter of about 650 B. t. u. is required.

Furthermore, in the delivery of natural gas by pipe line companies todistribution companies, the contracts almost invariably prescribemaximum delivery rates; so that an auxiliary supply of peak shaving gasis absolutely necessary.

2 Even in those cases where the demand by the distribution company ispermitted to exceed the maximum delivery rate specified in the contract,the charge per unit volume for the excess gas required to be supplied bythe pipe line company will ordinarily be substantially greater than forthat supplied just below the maximum delivery rate agreed upon.

A primary object of our invention is to provide novel methods of andapparatus for accomplishing the desirable results aforementioned.

Another object is to provide for use of any required volume of the peakshaving gas without deleteriously affecting the combustion or burnercharacteristics of the final mixture.

Another object is to minimize the required quality or heating value ofthe peak shaving gas when supplied.

Another and more specific object is to provide methods of and apparatusfor. automatically varying the quality of the'peak shaving gas inaccordance with variations in the proportionality or volume thereofrequired to be supplied.

Other objects and advantages of the invention will hereinafter appear.

The accompanying drawings illustrate certain embodiments of ourinvention which will now be described; it 'being understood that theinvention is susceptible of embodiment in other forms within the scopeof the appended claims.

In the drawings,

Figure 1 illustrates schematically and diagrammatically a fullyautomatic peak shaving gas mixing control system constructed inaccordance with our invention.

Fig. 2 illustrates a modified and simplified form of our invention,wherein a flow of peak shaving gas is effected at all times for mixturewith the base gas flow, the percentage flow' of peak shaving gas beingnormally maintained low enough to avoid the necessity for any excess inthe total heating value per unit volume thereof with respect to that ofthe base gas; the system of this figure including a hand set selectorwhich not only controls the proportionality of theflow of peak shavinggas with respect to the base gas, but also effects the setting of theassociated means for control of the total heating value per unit volumeof the peak shaving gas.

Fig. 3 is a graph illustrating theincrease required in the minimumquality or heating value mixture with a base gas, such as carburetedWater gas of 540 B. t. 11. per cubic foot, whereby satisfactory burner.performance of the complete.

mixture is insured, and

Fig. 4 illustrates another form of our invention which is functionallyquite similar to that shown in Fig. 2.

Referring to that form of our invention illustrated in Fig. 1, thenumeral l0 designates a conduit throughwhich gas from a suitablerelatively high pressure source is supplied to a line or conduit,designated by numeral II, for distribution to consumers. The gassupplied through conduit It may be of any suitable char; acter, such asnatural gas, carbureted water gas, or the like. This gas willhereinafter be referred to as the base gas which will normally havepre-. determined substantially constant values of: total heat per unitvolume, density and combustion characteristics. By way of example, itwill be assumed that such base gas consists of a typical carburetedwater gas of 540 B. t. u. per cubic foot.

Conduit lllis provided with afixedorifice. I2, 2. hand set valve I3, afirstpressure regulator, des ignated in general by numeral l4; andasecond pressure regulator l5.-, which, is inthe form of a. pressuredifference.regulator. Eegulator I sis. of a known form wherein the valveportion (not shown) is. adjustably biasedatQW n'd fully, openedposition;the regulaton including a diaphragm He whose upper surface is subjected;throughpipe M to the pressure ofzgas atthe downstream side of orificel2. Regulator. |4..thus serves to initially control thedistribution.pressure, within conduit ll. As. the required flow (to meetthe demandfrom conduit ll): approachesa preselected max-i mum value, as.indicated. by the orifice. meter (comprisingorifice t2; pipes [Wand 15anddiaphragm l5), thepressure drop across the orifice. l2 and hand setvalve [3 approaches the prese-. lected setting of thepressure diilerenceregulator l5, whereupon the. regulator l5. moves auto: matically. towardclgsed. position, thuslimiting, the. flow to establishafi-xed-orconstant pressure drop. across the orifice l2; and hand setvalve i3- jointly. Inasmuch as the amount of restriction is fixed byvalve [3 and orifice. I2, suchconstant pressure drop determinestherateofflowof. the gas in conduit 10, andif thisflow isinsufiicientto satisfythe demand; the. distribution pressurelin conduit H) willfall. Inattempting to compensate for'thisfall in pressure, the. valveassociatedwith pressure regulator 14 may go. toward or to its fully openedposition, but. this will-notafiect thefiowoigasthrough conduit l0,because the control of fiowhasbeen takenoverby the. pressure differenceregulator l 5- Thus upon proper adjustment of valve lBrand adjustment orcalibration of. pressure. difference regulator IS; the. samewillcooperate with orificel2 to limit. themaximuin volumetric rate. of flowof gas throughconduit ill' toconduit H, inaccordancewith the. contract.with a pipe line company, as. aforedescribed. It. follows. that, if: therate of; demand from the distribution line-ll is greater than theaforementioned maximiun volumetric rateof supply. through conduit. [0,thegas pressurein line. will fall below: the predetermined desiredpressuretherein. Therefore it is. necessary to provide an auxiliarysupply of-gas, suitable for mixture with-the. base gas supplied throughconduit l0;; to satisfy the demand for gasbeyond said maximum volumetricrate of sup; ply of the base gas, and-to-maint ain a substanl pns t, P sre. th s l' llillQidfiIi? u iq ine. I

In Fig. 1 we have illustrated means operable. automatically to supplythe additional. volumeoj gas to meet the excessive demand fromdistribution line H, whereby the pressure in the latter is maintained ata predetermined substantially constant value. The means now to bedescribed are also adapted to act automatically to control the qualityor total heatingyalue per unit volume of the auxiliary supply of-gasat-aminimum value (which, however, will under no conditions be less than thequality or total heating value per unit I volume of the. base gas) thusminimizing the excess. in quality or richness of the gas supplied todistribution line H when the demand is greater than the-predeterminedmaximum rate of supply of base gas. Such minimized quality of theauxiliary supply of gas is likewise automatically varied, in accordancewith variations in the rate of demand, in such a manner as to insureagainst improper combustion characteristics of the gas at the variouspoints of consumption.

It may be assumed, for example, that conduit lilr is connected with a.highpressure. source of supplyof 'basegasof 540.3. t. u. per cubic foot;the aforedescribed elements. l2, l3xand l4 acting to normally insure apredetermined relatively lower prcssure'of thegaswithin distributionline i i. Further itmay'beassumed that the auxiliary gas (propane, forexample) is. supplied to a conduit v H5.- at; a pressure.normally-substantially higher than the. predetermined relatively lowpressure which it is. desired tomaintain inthe distribution line I hAssociated with. conduit I6 is a so-called low pressure gas regulator.ll of known form, which includes a valve. (not shown) which is normallybiased to openposition-to provide a. free flow of thepropane into the.portion 16 of conduit I6. However, a. pipe. [8; affords communicationbetween theconduit. [that the downstream side of orifice l2. andthechamber- [1 which opens to the upper surfaceofa diaphragm H thearrangement being suchthat the valve of regulator i! will be. maintainedclosed so longas the pressure. in distribution conduit ll does not fallbelow the pressure preselected therefor. Upon a decrease in the.distribution pressure below said preselected value, as aforedeseribed,the valve of regulator H will open, thus providing a flow of propanethrough conduit portion I6 which in turn results ina pressure dropacross'the butterfiy valve. l9. Valve I9 is connected by suitablelinkage 20, 21 and 22' with a butterfly valve 23 located in the air lineor-conduit 24; said valves preferably being arranged at like angles; ineach of their various positionsduring joint operation thereof. The meansfor effecting movement of valves 19- and 23 comprises; linkage 25 and26; link zit-consisting ofa rodattachcd to a piston 21, which is movabletoward one end or the other of a cylinder 28-underconditions;hereinafter described.

Conduit 24 has its left-hand endconnected with any suitable source ofair under pressure; such source being represented in Fig. 4 by apower-driven bloweror pump designated by immeral 29, the-inlet end ofwhicl is shown at 29*. Located within conduit 2415a shut-off'valvc 30of'known form, which is-normally biased to its closed position asbymeans of a spring (not shown), orthe like. A chamberflll above adiaphragm 3i) is connected by pipe 3| witha threeway solenoid-operatedvalve 32, the operatingcoil of which is designated by numeral33. Whencoil 33gis deenergized valve 32 is adaptedto move to apositionwhereinpipe 3-! is vented to atmosphere,

h Qughanipeor opening 34, andto disconnect from pipe 3| the supply ofair under pressure, through pipe 35, from the conduit 24 at the lefthandside of shut-off valve 30. Pipe 35 preferably has located therein apilot regulator 36 of known form, whereby the pressure of air suppliedto valve 32 is limited to a predetermined value. However, when coil 33is energized, as illustrated, valve 32 acts to disconnect pipe 3] fromvent 34 and to connect the former with pipe 35, Whereby valve 30 ismoved to fully open position against the normal bias thereof.

Also located within conduit 24 at the upstream side of butterfly valve23 is a pressure diiference regulating valve 31 (substantially like theregulator l5 aforementioned), the same having pipes 31 and 31*respectively connecting the conduit 24 at the upstream and downstreamsides of butterfly valve 23 with the chambers at the lower and uppersides of a diaphragm 31.

Thus, assuming that valves l9 and 23 were in fully closed position atthe time the valve of regulator I! was opened (due to a decrease inpressure of the gas in distribution line H, as an incident to anincrease in demand beyond the permissible volumetric rate of flow of thebase gas), the element 38 carried by the aforementioned link 26 willhave acted upon the normally closed limit switch 39 to effect openingthereof, with consequent deenergization of coil 33, for the purposeaforedescribecl.

A fluid pressure operated ratio controller 40, of the general characterdisclosed in Wunsch Patent No. 1,558,529, dated October 27, 1925, andmore particularly of the character shown in Fig. 1 of Schmidt and BricePatent No. 1,999,740, granted April 30, 1935, is employed to effectmovement of piston 21, with consequent joint operation of valves 1 9 and23. More particularly, the pipes 4| and 42 respectively affordcommunication between portion [6 of conduit I6 at the upstream anddownstream sides of valve I9 and the lower and uppers sides of adiaphragm 43; whereas the pipes 44 and 45 respectively affordcommunication between conduit 24 at the upstream and downstream sides ofvalve 23 and the upper and lower sides of a diaphragm 46. Because thevalve 30 is closed, as aforedescribed, at the time of opening of thevalve of regulator 11, there will be no pressure drop across the airline butterfly valve 23, so that the resultant pressure drop acrossvalve 19 will act in a well known manner to effect movement of piston'21 toward the left. Such movement of piston 21 not only eifectsmovement of valves [9 and 23 jointly from their closed position, but theresultant movement of element 38 toward the left also permits limitswitch 39 to move to its normally closed position, as illustrated. Theconsequent opening of shutoff valve 3!] permits air to flow throughconduit 24; the pressure diiference regulator 3! in conduit 24controlling the pressure drop across butterfly valve 23 to maintain saidpressure drop of substantially constant valve. If the pressure dropacross the low pressure gas butterfly valve l9 continues to exceed thepressure drop across the air line butterfly valve 23 the duplex valvesI9, 23 will continue to open jointly until said pressure drops areequalized; with the volumetric rate of flow of the mixture of lowpressure gas (propane) and air through conduit 41 of the value necessaryto maintain the gas pressure in the distribution conduit 11 at thedesired value, for which the low pressure gas regulator l'lis set. Asthe demand for peak shaving gas (from conduit 41) decreases, due to adecrease in the demandfor gas from the distribution linev I I, theduplex valves [9 an'd23 will move jointly. toward their closed positionsand eventually shut off the flow of low pressuregasthrough portion I6 ofconduit [6 and the'flow ofairthrough conduit 24; the limit switch'39being opened, as anincident to closure of said valves 19' and 23', todeenergize coil33, 'with resultant closure of the shut-off valve 30 inthe air line 24.

It is obvious that when peakshaving gas is being added to thedistribution conduit 1 I; the rate of flow of the base gas throughconduit 10 is at a preselected maximum 'value; and that, therefore, thevolumetric rate of flow of the peak shaving gas is definitely related tothevolumetric rate of flow of such base-gas.- Inasmuch as the pressuredrop across the air valve 23 is maintained at a constant valve, by thedifferential pressure regulator 31, the position of the valves l9 and 23jointly affords a definite indication of the volumetric rate of flow ofair, which in turn is definitely related to the volumetric rate of flowof the peak shaving gas (propane-air mixture flowing through conduit41). Said volumetric rate of flow of the propane-air mixture thendetermines the minimum heating value thereof which will afford asatisfactory mixture when the same is combined with the base gas flowingin distribution line H.

In accordance'with our invention a continuous sample of the peak shavingpropane-air mixture flowing in conduit 41 is withdrawn and suppliedthrough pipe 49 to a suitable calorimetric device, such as that shownschematically at 49. The calorimeter 49 is preferably of thequick-acting type disclosed and claimed in the Schmidt Patent No.2,002,279, granted May 21, 1935, for Calorimetric Method andApparatusAdapted for Gas Mixing Control. Calorimeter 49 has associated therewitha peak shaving gas B. t. u. scheduling rheostat 50 (which is properlydesigned to provide resistance values, at different points in the rangeof movement of contactor 50, which will correspond substantially exactlywith the required minimum heating values of the peak shaving gas,according to the percentage of the latter in the total flow of gassupplied to distribution line H, Fig. 1). 'Suchrequired variations in B.t. u. per cubic foot of the peak shaving gas in accordance withvariations in the rate of demand for. the latter'are illustratedgraphically in Fig. 3 hereof, as hereinafter more fully explained. I

By linking the contactor 50 of rheostat 50, designed and/or calibratedin the manner aforedescribed, with the operating mechanism for theduplex valves l9 and 23, as indicated at5l in Fig. 1, the total heatingvalue per unit volume of the peak shaving propane-air mixture, suppliedthrough conduit 41 to conduit II, will be maintained at the minimumvalue which will not cause trouble on gas burning equipment when mixedwith the base gas in the predetermined variable proportions establishedby the gas mixing control equipment illustrated in Fig. 1. Suchequipment will therefore deliver to the distribution line H either basegas or a mixture of base gas and peak shaving gas with the minimumheating value which will not cause defective burner performance. Theadvantage of this arrangement; when -tliecombinedfiows of base gas andpeak shaving' gas are 's'old on a volumetric bas1s; is apparent." I Y 1l As shown in Fig. 1, thecalorimetric device 49 acts, if necessary, 'toeffectoper'aftion' of a splitfield reversible motor' 52 inone'directionor the other; motor 52 acting, through suitableispeedreducing gearingrepresented by numeral-52 and a. worm Iz todrive a nut: 53, which isattached to a rodzfl- 'tor adjusting the. position .of a slider (not:shown) ,of ,thecharacter illustrated in :Fig. 1 of said, Schmidt-and:Brice Patent No. 1,999,740; whereby the volumetric proportionality .ofthe flow of low'pressuregasin-portion I E ofconduit I6 is varied withrespectto thevolumetricrate or flow otair in conduit. By this means :thetotal heating valueper unit volume .of the peak shaving as mixtureflowing: conduit 47 is definitely controlled, in accordance with thevolumetric rateof flow thereofixin a. manner to minimizethe'heatlngvalue. thereof under various conditionsgraphically.depictedin Fig. 3.

Ii thebase gas only'ifrom conduit I0. in. Fig. 1 is sold. and the.ultimate consumer supplies the peak, shavin .gas, ithesame' controlsystem could be. used; butin such aninstallation changes inv the -peakshaving gas heating value schedule wou d either be, .unnecessary .or therequired changes would be relatively small. However, in certain criticalburner applications at least minorcontrolled variations-in the peakshaving gas heating value would be desirable. Thedesired-variationswould again be related to proportionalities of--flows, and would correspondingly be related to the aforementionedjointvariations i he po itions oi the. duplex valves [8; and 23.

Although: we havespecifically descr'ibed. our invention as applied. to.a system involving the e f carbureted Water-gas as the bas it is to beunderstoodgthatthe invention is adaptable for; usein systems wherein,the base gas is other than, carburetediwat r as. Thus if t basegasconsists of natural; gas, a relationship of volumetric proportionalityand total heating value per unit volume of the. peak shaving gas mixturewith respect thereto similar to-tha-t, illust d i Fis-v 3 willzapply; exept...of course. that the magnitude of the t al hea n values p r unitvolume of thebase and peak-shaving gases will be higher.

Various slight mod ications i theform and arrangement of the partsofjthecontrol system illustrated in l will at once suggest themselves tot-hoseskilled in this art. For example, a high pressure air storage tankmight. be substituted for the blower 2 9 shown inEig. l. Varione wellknown accessorifis-ln ght also be :in-

corporated in, the as :mixingcontrolsystem. For example, a pressureresponsive. alarm switch might be associated with conduit lfl'tojindicate a failure of pressureofqthe. base gas supply. Similarly,lcnownforms of shut-oil devices, might be associated with the conduits15,12 and 4:1.

o r po t0- f: i1. reof pr ssure of the peak shaving gas or vapor.

Referring more particularlyto 3,:we have graphically illustratedthe-variation requiredain the total heating value per-unit volume of 'apeak shaving gas-air mixture of the-character herein specified,according to the required varia tions in the percentagepj the totalvolumetric rate of flow (to distribution rhneljl in-Eigil. for example)which must be composed of. the peak shaving gas-a-ir mixture toisatisfythe rate of demand from the distribution line; Thus the abscissa 55.bears legends 0. in icateth 'p centage of the total volumetric rate offlow of the base gas and the-peakshavi I :-gas-air;mixture which mustconsist of thedatter inmrder to satisfy the demand. The.ordinate-flfibears ends to indifla the .requiredqualitye imumtotal-hcating value' per: unit volume, of the peak shaving gas-airmixture supplied for use inconjunction with a base gas having asubstantially constant total heating value of 540 B. t. u. per cubicfoot, as aforedescribed.

As indicated by the horizontal portion 51 of the graph, if the peakshaving gas-air mixture comprises fifteen per cent or less of the totalvolumetric rate of fiow, the quality of said peak shaving gas-airmixture may likewise be maintained at approximately 540 B. t. u. percubic foot without deleteriously affecting the combustioncharacteristics of the final mixture at the consumers appliances. Thecurved portion 58 of the graph illustrates the gradual increase in therequired total heating value per unit volume of the peak shaving gas-airmixture, as the latter is required to constitute a larger and largerpercentage of the total volumetric rate of flow. Thus if one-half of thetotal volumetric rate of flow is required to be of the peak shavinggas-air mixture, the total heating value of the latter must be increasedto 650 B. t. u. per cubic foot, as indicated at the point 58 in Fig. 3,and so on. Moreover, as aforestated, each oi the total heating values ofthe peak shavin gas-air mixture indicated in the graph of 3 is theminimum value which we have f ound by experiment is satisfactory for ourpurpose (in that it has no deleterious effect upon theoperation of thevarious types of consumerappfifihflfis and in no case requires anyreadjustment of the latter) Such minimum value in each instance, ofcourse, correspondingly reduces the cost to the gas distributing companyof the additional gas required to satisfy the peale or abnormal rates ofdemand when they occur. Also, as aforeindicated, such minimum totalheating value of the peak shaving gas-air mixture is in each instancesubstantially lower than the theorz tically correct value, with acorresponding saving to the gas distributing company. 1

In each of Figs. 2 and 4 we have illustrated modifications wherein aflow of peak shavinggas at all times is contemplated; the volumetricproportionality of such how, with respect-to that of the base gas, beingpreselected and maintained under conditions of variation in thevolumetric rate of flow of the base gas as an incident to variations inthe rate oi demand from the distribution line. Such an arrangement isdesirable where the demand {or gas in excess of the maximum base gassupply over an extended period can be anticipated. For example, let itbe-assumed that a given gas plant has -a twenty-four hour capacity of240,000 cubic feet, whereas it is estimated that the -d emand during thenext twenty-four hours will be approximately 264,000 cubic feet of .gas.By introducing peak shaving gas throughout such twenty-four hour periodat a volumetric rate of flow equal to ten per cent of the total gas flowrequired to meet such demand it is-possible, as aforedescribed, to havethe peak shaving gas of a total heating value. per unit volume .the sameas that of the base gas. In contrast withthis, if the totalrequiredamount of peakshaving gas were introduced during only a part (that is,the portions of peak demand Ijor gas) of the twenty-four hour period,the percentagesofpeak shaving gas would, of course, be substantiallyhigher, and would likely require an increasein the total heating valueper unit volume of the propane-air mixture, in order to avoid trouble onconsumer appliances. 7

With such an arrangement it is, of course,

assumed that in a system-wherein the instantaneous volumetric rate ofdemand for gas is subject to relatively wide variations, 9. storagecontainer for the temporary excess volumes of the mixture of base gasand peak shaving gas or of the base gas alone would be provided, inorder to take full advantage of the maximum capacity of, the base gasproducing plant throughout the entire period. 1

Referring more particularly to Fig. 2, the numeral 58 designates'aconduit through which the base-gas is adapted to flow, either directlyfrom a producing plant of the aforementioned capacity, or from a storagecontainer associated with such plant. A so-called butterfly valve 59 islocated within conduit 58, said valve being adapted to act as a meteringdevice. Valve 59 is adjustable automatically to maintaina preselectedvalue of the pressure drop thereacross. The adjusting means comprises alever 60 rigidly attached to valve 59, and a lever 6| pivotallyconnected to lever 69 and to a rod 62 attached to a piston 63; thelatter being slidable within a cylinder 64. Pipes 65 and Gilead fromopposite ends of cylinder 64 and have their outer ends arranged adjacenteach other for cooperation with a movable jet or nozzle 61, which isconnected with a source of fluid under pressure, as disclosed in theaforementioned Patent No. 1,999,740. 4

Pipes 68 and 69 are connected between conduit 58 at the upstream anddownstream sides of valve 59 and the lower and upper chambers associatedwith a diaphragm I0. A stud Ill attached to diaphragm H! has its endengaging the lower side of nozzle 61; a coiled spring II beinginterposed under compression between the opposite side of nozzle 61 andan abutment in the form of a manually adjustable screw or bolt I2.Assuming that the base gas is supplied to conduit 58 at a predeterminedsubstantially constant pressure, it will be apparent that upon a givenadjustment of screw I2 the valve 59 will be opened automatically to adegree necessary to maintain the preselected pressure drop thereacross,under conditions of variations in the rate of demand for gas from thedistribution line I3.

The conduit I4 is adapted to be supplied with peak shaving gas (such aspropane) from a suitable source, said conduit having therein a butterflyvalve and a butterfly valve 16. An air conduit 'II is supplied with airunder pressure from a suitable source, such as the motor operated bloweror pump I8; said conduit I'Ihaving therein a butterfly Valve I9. ValvesI6 and I9 are of the duplex type, whereby the same when moved jointlyare adapted to assume corresponding angular positions within theirrespective conduits. Thus said valves have rigidly attached thereto thelevers 80 and BI, which are pivotally connected with a lever 82; thelatter havingan integral upper end portion 82 which is pivotallyconnected with a lever 83. Lever 83 is pivoted at 83 to a fixed support.A second oppositely extending lever 84 is pivoted at 84* to a fixedsupport. A pair of levers 85 and 86 are pivotally connected to eachotherand respectively to the lever 89 and the valve 59.

An adjustable slider block or roller, 81 is interposed vbetweenthelevers 83 and 84, as shown.

The arrangement ispreferably such that with rollertl moved toward theright to a position in substantially'vertical alinement with the lowerend of lever 85 and the upper end of lever portion 82* each of thevalves I6 and I9 will assume a rotary or angular position exactlycorresponding with that, of valve 59. Also with roller81 in suchposition any degree A of. movement, of valve 59 toward fully open orfully closed position will effect corresponding movement of valves I6and I9 jointly. As shown, lever 83 is at all times biased toward lever84, as by means of a headed rod or bolt 88 attached to lever 84, with acoiled compressed spring 89 interposed between the bolt head and theouter surface of lever 83.

In like manner, if roller 81 is moved toward its extreme left-handposition, as illustrated, the valves (-8 and 79 will be moved towardmore nearly closed positions than'the valve 59 when the latter is in afully openedflor partially opened position. Adjustment of roller 81 maybe effected at will in any suitable manner, as by means of a pair oflinks or rods 90 and 9|, which are preferably pivotally connected at 99,rod 99 being at-, tached to roller 81 androd 9| having a screwthreadedright-hand end 9I which is adapted to cooperate with an internallythreaded nut 92 which is held captive between a pair of abutments 93 and94. Nut 92 is provided with an intermediate enlargement 92 to facilitatemanual rotation thereof. A rod 95 has a screw-threaded end 95 forcooperation with the other end of nut 92; so that as the rod 9l movesendwise in each direction the rod 95 will move endwise in an oppositedirection. Rod 95 is slidably supported by a perforated lug upon asuitable member 96; the right-hand end of rod 95 having a, contactor 9!attached thereto and insulated therefrom, as diagrammaticallyillustrated at 98; said contactor 91 being adapted to cooperate with apeak shaving gas B. t. u. scheduling rheostat 99 of the aforementionedcharacter shown at 59 in Fig. 1.

As shown in Fig, 2, the valves I5, I6 and I9 are operable automaticallyin a well known manner to normally insure a predeterminedproportionality of the volumetric rate of flow of propane throughconduit I4 with respect to the volumetric rate of flow of air throughconduit TI. Such flow proportioning means is in general like that shownin Fig. l of the aforementioned Patent No. 1,999,740, to which referencemay be had for a more detailed description of the construction and modeof operation thereof. Thus I have shown a device I09 which comprisesessentially a nozzle [88 the instantaneous position of which iscontrolled in response to the differential value of the pressure dropsacross valves I6 and I9, as ascertained by diaphragms Illll and I00. Thelower and upper sides of diaphragm [00 are subjected to the fluidpressures at the upstream and downstream sides respectively of valve I6,through the medium of pipes I90 and I99 whereas the upper and lowersides of diaphragm Hill are subjected to the fluid pressures at theupstream and downstream sides respectively of valve I9, through themedium of pipes I99 and lfifl A slider block N19 is" initially manuallyadjusted to provide the required proportionality between the volumetricrates of flow of air through conduit 'Il and propane through conduit 14to afford a mixture of the desired total heating value per. unit volumeflowing through conduit I 91 for mixture with the base gas flowingthrough conduit 58. Thus if said base gas has a total heating value perunit volume of .540 B. t. u. per cubic foot, the peak shaving gasflowing in conduit I91 will normally have the same heating value.Moreover, if the rate of flow of base gas is increased through fartheropening of valve 59 to satisfy an increase in the rate of demand fromconduit. 13, the means aforedescribed will act toefiect a proportionaldegree of opening valves I9. and I9. Such opening of valve I9 willimmediately result in a correacoai'ee sponding increase in zit-he .rateof 'flow f .air

through conduit '11, :and the .device LL90 :will

.rate. of flow of propanegthusirestoring and mainitaining thepreselected proportionality of the :flows of air-and propane.

The peak :shaving gas 13. t. u. scheduling rheostat-. 99 .isdesigned andcalibrated in the .manner set P forth in the description of rheostatfEBof 1.

Ihat isto say, if it is desired-to maintain 'ithe volumetric rate offlow of peak shaving gas, through conduit 1 01, at a value corresponding{to ten per' cent (or not more than fifteen --per-cent) of thevolumetricrate of now throughdistribution line 13, the rheostat da -will haveno:efieet upon-the total heating value per' unit volume of the peakshaving gas' suppliedtosaid conduit I01. On the other hand, thecalorimetric device 49 (like that described in -Figi 1) will act'inresponse to any variations in the total heating value of thesampleextracte'd through pipetS to efiect proper proportioning'of the'-volumetric rates of flow of 'air '(thro ugh conduit '11) and propane(through conduit 1-4) to maintain-the same at the value preselectedtherefor; any such adjustment being eiiectedaritomatically'by motor 52acting (through elements 52 '52?, 53 and 54) upon slider block 100 "inthe well known manner.

Inthe device of i Fig. 2-it isto be-understood that the butterfly-valves5116, 1,9 and are so designed that 'a predetermined degree of rotary orangular movement of thedisks thereof will client a correspondingpercentage change in fluid flow ,therethrough. The valve '59 in the basegas conduit-58 will therefore assume an angular position proportional tothe volumetric rate of flow of gas through conduit 58, and this positionis normally transmitted to the valves 'lfiand 19 in the propane and airlines,through"thejmedium of the levers 83 and 84 and interposedjrolleror slider 81, when the latter is inits aforementioned neutral position.With valve ,59 closed the arrangement is such that valves '18 and [9would also be closed. With valve '59 fully opened the duplex valves ".6andls would be opened toadegree depending upon the position of the "handset roller or slider'block 81 which has associated therewith theaforementioned rheostat 99.

The pressure in the conduit '13'is normally maintained at somepredetermined distribution pressure by any suitable means (not shown inFig. 2) in conduit 58. The air blower I8 supplies ,a substantiallyconstant discharge pressure, so that the ,fiow of ,air is determined bythe ,position'of the duplex valve 79 in the air line TI. The flow,controlvalve 15 in the propane line '14, actuated by piston [00 controltheiiow of propane at a rate to establish a pressure drop acrossltheduplex valve [6 which is proportional to the'lpressure drop across thevalve 19. The-exact proportionality of air and propane pressure drops(and rates of flow) is adjustable over a fixed range by the motoroperated adjuster I00, the operation of which is controlled by thecalorimetric device 49. The control point of the latter is in turncontrolled by the rheostat 99 associated with roller 81, which ismanually preset at the desired position.

Assuming that it is desired to have the pro- 132" pane-air mixturesupplied -through conduit !;0 I; constitute ten per cent of: thetotalivolumetric rate of flow through. distribution line "|r3;iit-.will

be understood that with thezvalves 1-59, 1B and 13 initially closed, themanual adjustment .of roller 8? and rheostat contactor ii'l .would notchange thesetting oi valves'l9 and' lS. However, as the metering valve59 movestoward fully opened position, under the influence of therequired volumetric rateof fiow of-base gas through conduit 58, theduplex valves "19 and 78 will open proportionately; the degree ofopening the latter depending upon 1 the preselectedrati'o setting(ofioller 'fll) and the degree of opening of metering valve 59 Withroller 8? so positioned that the peak shaving gas supplied from conduitlfll forms ten per cent-or less ofthe mixture flowing in distributionline i3, the rheostat 419 would then maintain the control pointsettingof the calorimetric device is? to provide a peak shaving gas-airmixture of a total heating value per unit volume substantially equal tothat of the base'gas flowing in conduit 58. However, when theproportionality of peak shaving gas is increased to more than fifteenper cent of the total flow through line 13, the necessary increase inthecontrol point setting of calorimetric device =49 is automaticallychanged as a'result of movement of rheostat contactor'sl as an incidentto adjustment ofroller 81.

The gas mixing control system diagrammaticaliy illustrated in Fig. 4 isfunctionally quite similar to that of Fig. 2. 'However, in Fig. 4 theconduit I92 through which the base gas is adapted to how is providedwith a 'metering device in the form of a fixed orifice 103. Any suitablemeans (not shown) "may be employed for insuring maintenance ofapredetermined pressure of the base gas atthe upstream side of orificeI93, whereby a predetermined pressure will normally be providedin thedistributionline, notwithstanding variations in the rate of demandfromthe latter. By way of 'an example, it may be assumed that the base :gassupplied from conduit I02 to distribution line 1,64 has a total heatingvalue per unit volume of 5,40,B.-t. u. per cubic foot.

The peak shaving gas, :such .as propane, is supplied from 'a suitablesource :to "conduit and air for mixture therewith 'is supplied, "byblower "N16, for example, to conduit I01. The peak shaving gas and airmix with each other during their flow through conduit 1.08 todistribution line I04. Conduits 105 and I0! are .respectively providedwith butterfly valves IDS land I it; said valvesbeing of'the duplextype; the same having like angular positions and the same (when moved)beingiconstrainedto move jointly to :like degrees through the'medium o1linkage .Hl, H2 and H3.

Conduits llliand I01 are also respectivelyprovided with valves 1 Hand,I;l,5,' w,hich are adjustable automatically to normally maintainsubstantially constant the preselected values of .the pressure dropsacross the respective valves .109 and H5 aforementioned.

Thus, a pair of pipes ITS andllgl .leadlfrom the upstream and downstreamsides .of .valve N19 to the. chambers at the upper and lower surfacesrespectively of a diaphragm-l I! having associated therewith a stud .Il9which engages the-upper side of a nozzle I 20 connected to a suitablesource of fluid ,under pressure. Nozzle 1 20 cooperates with theadjacent open ends .of pipes HI and I22 leadin to opposite ends ofacylinder 123 having therein a piston I 24; the latter being connectedby rod I25 and link I26 with lever I 21 attached to valve I I4. A springI28 is interposed between the lower side of nozzle I20 and an adjustableabutment I29. The degree of compression of spring I23 may be initiallymanually adjusted in any suitable manner to preselect the value of thepressure drop across valve I09, and hence the angular position of valveII4 for any given adjustment of valve I09. Normally, however, the degreeof compression of spring I28 is merely subject to automatic control byoperation of a reversible electric motor I 30 through the medium ofreduction gearing I3I and an associated crank I 32, to effect either anincrease or decrease in the degree of compression of spring I28. MotorI30 is in turn subject to control by the action of a calorimetric device49, like that of Figs. 1 and 2, to normally maintain the mixture of peakshaving gas and air at the aforementioned total heating value of 540 B.t. u. per cubic foot, so long as the volumetric rate of flow thereofdoes not exceed fifteen per cent of the total volumetric rate of flowthrough distribution line The valve H5 is likewise adjustedautomatically in response to automatic adjustment of valve IIO (jointly withvalve I09), whereby the pressure drop across valve I I is maintainedsubstantially constant and normally proportional to the pressure dropacross valve I09. The means associated with valves H0 and H foreifecting such adjustment of the latter are, for the most part,identical with the elements associated with valves I09 and H4, asindicated bycorresponding numerals of reference. However, thecompression spring I28 is interposed between the lowerside of nozzle Iand a manually adjustable abutmentin the form of a screw or stud I 33;the latter being manually adjusted .upon installation ofthe system to soproportion the flow of air through conduit I0'I as to provide thedesired total heating value perunit volume of the mixture flowin inconduit I08, when the volumetric rate ofiiow of the latter does notexceed fifteen per cent of the total flow through distribution line I04,

Means are provided for normally automatically insuring that thevolumetric rate of flow of peak shavinggas through conduit I08 shallconstitute a preselected proportion (say one-tenth) of the totalvolumetricrate of flow through distribution line I04. Said meanscomprises a pair of pipes I34 and I35 respectively connected withconduitI02 between the upstream and downstream sides of orifice I03 and thechambers at the upper and lower surfaces of a diaphragm I36. A stud I3!is attached to and projects downwardly from diaphragm I 36 forengagement with the upper side of a nozzle I38 connected in the usualmanner with a source of fluid under pressure. A coiled compressionspring I39 is interposed between the lower side of nozzle I38 and anabutment I40, which is adjustable automatically in the mannerhereinafter described. Assuming a givenadjustment of abutment I40, thearrangement is such that upon a variation in the volumetric rate of flowof base gas through conduit I02 the associated means will provide for acorresponding or proportional variation in the volumetric rate of flowof peak shaving gas through conduit I08, so that the percentage quantityof the latter will be maintained constant at the value preselectedtherefon a Thus, in' the event of an increased demand from distributionline. I04, the pressure at the'do'wn- 92 to' facilitate manual rotationthereof.

'14 stream side-of orifice 103 ,would belowered, and asaconsequence'di'aphragm I36 would effect downward movement of stud I31to bring nozzle I38 into'partial or full alinement with the end of a.pipe jI 4I leading to the, left-hand end of a cylinder I42, withresultant movement of piston I43 toward the right. ,Upon such movementof piston fl'43-the cam member I55 attached thereto will automaticallyeffect adjustment of abutment I40gto increase the, loading of spring I39until the "jet .I38 ;is restored to neutral position; in this' mannerinsuring the required degrees of opening of ;the respective valves I09,I I4 and I I0, I I5 topro vide the required volumetric rate of fiow ;ofthe, propane-air mixture fromconduit I08 to distribution line I04to meetthe'demand from the; latte r.-;v As ;will be apparent, suchincreasedrate ofrfiow of the propane-airmixture will restore the desireddistribution pressure in line I04. Piston rod I44 has a pin and slotconnection I45 witha lever having angularly arranged arms-I45and I41 anda'fixed point of pivotal support at I48; Arm I4'Iis so arrangedwithrespectto alever I49 -(having a fixed pivot at I50)- that any; up ordownmovement of arm I41. is transmitted to said lever I49. Such movementis transmitted: through; the'medium of a manually adjustable sliderblock in the form of a roller I5I;- suitable means, such as a headedstud, I52 and a coiled compression spring I53 being interposed betweenarm I41 and lever I49 to resiliently bias the latter and roller I5Itoward arm- I4'I.

Under the condition last mentioned'the downward movement oi arm; I41 andlever I49 will be transmitted, through-a lever I54 to the aforementionedlevers; I I3, II 2 and III, to efiect the required degree 'ofjointmovement of valves I09 and I Illtoward fullyopen position to provide thedesired increase inthe volumetric rate of flow of peak shaving gasthrough conduitl08; the aforedescribed means acting automatically toeffect the necessary movements of valves I I4 and I I 5 to maintain thetotal heating value per unit'volume of the peak shaving gassubstantially constant.

In the event that it is desired to increase or decrease the volumetricproportionality of the.

peak shaving gas flowing through conduit I08 (with respect to the totalvolume flowing in distribution line I04) this may be efiected bymanually adjusting the positionof roller I5I with respect to armI4'I-and levr'l49., Thus roller I5I has attached thereto a yoke memberI5I which is pivotally connected at I5I to a rod 9I, whose right-handend 9I' isscrew-threaded for cooperation with a rotatable nut 92. Nut 92is held against endwise movement between a pair .of fixed abutments''93, and 94, as described in connection with the system of Fig. 2. Nut"92 isshown as provided with an enlarged portion Also, as shown, nut 92is adapted for simultaneous cooperation with'the threaded end 95 of arod 95, which has attached thereto (but insulated there- :from,'as'indicated at 98) a contactor 9? for cooperation with the resistanceof rheostat 99.

rheostat contactor 91 will be such as to set the calorimetric; device 49to. maintain a predetermined higher total, heating value of the peakshaving gas flowing-in conduit 1108, as indicated by the valuesgraphically illustrated in Fig. 3.

1. In a- -method-of control of gas mixing for peak shaving, the-stepswhich comprise, effecting a fiow of base gas having a predeterminedsubstantially constant. total heating value per unit volume at avolumetric rate variable with the rate of demand of a distributionsystem to provide a predetermined substantially constant pressure-in thedistribution system effecting a flowof peak shaving gas at a pressuresubstantially corresponding to that aforementioned 'to supplement saidflow 'of base gas, to thereby substantially increase the-flowoi gas tothe distribution-system, said peak shaving gas having a total heatingvalue per unit volume substantially correspondin 'to thatlo'f saidfbasegas when the volumetric rate of flow of peak shaving gas does not exceedapr'ede'termined proportion of the total flow throug'hsaid-distribution'line, whereby the mixtureof base and peak shavinggases will have the desired combustion characteristics, andincreasingthe total heating value perunit volume of said peak shaving'gas .for the purpose last mentioned, in aceordance with a predeterminedschedule, when said peak s'having'gas-exceeds said predeterminedproportion of the total flow through said di'stribution'lin'e, saidschedule being such as to minimize the excess in total heating value perunit volumeof the mixture of base and peak'shavi'n'g gases.

2. In a method of control of gas mixing for peak shaving, thestepsWhich-comprise efiecting a flow of'base gas at a predeterminedsubstantially constant pressure and of a-predeterminedsubstantiallyconstanttotal heating value per unit volume, at a'volumetric rate corresponding to the rate of demandth'erefor fromadistribution line, said base gas increasing in price per unit volumeabove "a certain volumetric rate of flow, and when the demand for gasexceeds said certain volumetri'ctrate of'flow of: base gas, maintainingthe flow of base :gas at said :certaini volumetric ratev of, flow whilesimultaneously effecti'ng a flow of'.:a..pea-k shaving gas ata pressuresubstantially"corresponding =to that aforementioned and -a;t a=:volumetric rate corresponding to the" dff'erence betweenthe of demandfor gas and said .cer-tain volumetric 'rateof how of base gas, tothereby =restore-,said substantially constant -pressure,.said peak.shaving gas having a'total heating value 'per unit volume atlea-st asgreat as 'thatof said'base gas.

3. In a methodorcontroi of gas mixing for peak shaving, the steps "whichcomprise, effecting a flow of base gas ata' predetermined substantiallyconstant pressureyand of'a predetermined substantially constanttotalheating value perunit volume, at a volumetric rate corresponding tothe'rate of demand therefor from a distribution line, effecting-a how ofpeak shaving gas at a pressure substantially corresponding to thataforementioned and at :a volumetric rate corresponding tothe differencebetween the. rate of demand for the base gas and a-maximum vol- 1.peakshaving gaseswi'll'ha've'the desired comb'ustioncharacteristicswhen used-in consumer appliances, and increasing thetotal heating value per unit volume of said peak --shavinggas for thepurpose last men-tioned in accordance with a schedule based upon thevolumetric proportionality .oi the peak shaving gas'with respect tothebase gas, whereby the excess in total heating value sper unit volumeof said mixture of base andipeak shaving gases may be minimized.

4. Ina gas mixing control system for peak shaving, in :combination, adistribution line, means for supplying l to said distribution line moreor less of a predetermined maximum volumetric rate of flow of a base gasof predetermined total heating value per unit volume, in accordance-withthe rate of demand for the latter, to normally maintain in saiddistribution line apressure of at least apredetermined minimum value, aseparate source of peak shaving gas, means responsive to a predetermineddrop in pressure-of the base gasinsaid distribution line, as an incidenttoademand-greater than the .volumetric'rate of supply of base gas tosaid line, to effectavolumetrierate of flowof peak shavinggas suchas torestore and maintain the desired minimum gas pressure in saiddistribution line, and said last mentioned means including meansoperable automatically in accordance with the proportional volumetricrate of flow of said peak shaving gas, with respect to the volumetricrate offlow of'base gas, to efiect'variationin the totalheating'valueper unit volume of said peak shaving gas in such a manner as to minimizethe excess of such value over-that required to atford proper combustionof the mixture of base and peakshaving gases in gas burners adjusted foruse of said base gas.

5. In a gas mixing control system for peak shaving, in combination, adistribution line, means for supplying to said distribution line aportion or all of a predetermined maximum volumetric rate of flow of abase gas of predetermined total heating value per unit volume,'inaccordancewiththe rate of demand for the latter, -to normally maintainin said distribution line a substantially constant predeterminedpressure, a separate source of peak shaving gas,

means responsive to a predetermined drop in pressure ofthe-base gas insaid distribution line, as an incident to a demand therefor greater thansaid maximum rate of flow thereof, to effeet a volumetric rate offlow'of peak shaving gas such as to restore and maintain the desiredminimum gas pressure in said distribution line,

and said lastmentioned means including means operable automatically inaccordance with the proportional volumetric rate of flow of said peakshavinggas, with respectto the volumetric rate offlow of base-gas, toeffect variation in the total heating value 'per' unit volume of said'pea'k-shaving'gas in such a'manner as tominimize the excess of suchvalue over that required to afford proper combustion of the mixture ofbase and peak shaving gases in consumer appliancesof various types.

means includingmeans acting in response to variations in-the rate ofdemand from the distribution line tonormallymaintain a predeterminedsubstantially constant pressure of-gas in the latter, means responsiveto a predetermined drop in gas pressure in said distribution line toeffectJaLflowing mixture of peak shaving gas -andair to:said:distribution'line-at such a volumetric rate as to restore theaforementioned pressure in the latter, and means for controlling thetotal heating value per unit volume of said mixture of peak shaving gasand air, whereby the latter when mixed with said base gas Will haveproper combustion characteristics when used in consumer appliances.

7. In a gas mixing control system for peak shaving, in combination, aconduit through which a base gas of substantially constant predeterminedtotal heating value per unit volume is adapted to flow to a distributionline, means in said conduit for limiting the maximum volumeric rate offlow of base gas therethrough, said means including means acting inresponse to variations in the rate of demand from the distribution lineto normally maintain a predetermined substantially constant pressure ofgas in the latter, means responsive to a predetermined drop in gaspressure in said distribution line to effect a flowing mixture of peakshaving gas and air to said distribution line at such a volumetric rateas to restore the aforementioned pressure in the latter, means forcontrolling the total heating value per unit volume of said mixture ofpeak shaving gas and air, whereby the latter when mixed with said basegas will have proper combustion characteristics when used in consumerappliances, and said last mentioned means including means for varyingthe total heating value per unit volume of said mixture of peak shavinggas and air, in accordance with the required variations in thevolumetric proportionality thereof with respect to the base gas, in sucha manner as to minimize the excessive total heating value per unitvolume of said mixture of peak shaving gas and air when supplied underall conditions.

8. In a gas mixing control system for peak shaving, in combination,means for effecting a flow of base gas having a substantially constanttotal heating value per unit volume at a volumetric rate variable withthe rate of demand of a distribution system to provide a predeterminedsubstantially constant pressure in the distribution system, means foreffecting a flow of peak shaving gas at a pressure substantiallycorresponding to that aforementioned to supplement said flow of basegas, to thereby substantially increase the flow of gas to thedistribution system, said peak shaving gas having a total heating valueper unit volume substantially corresponding to that of said base gaswhen the volumetric rate of flow of peak shaving gas does not exceed apredetermined proportion of the total flow through said distributionline, whereby the desired combustion characteristics of the mixture ofbase and peak shaving gases when used in consumer appliances areinsured, and means for increasing the total heating value per unitvolume of said peak shaving gas for the purpose last mentioned, inaccordance with a predetermined schedule, when said peak shaving gas exceeds said predetermined proportion of the total flow through saiddistribution line, said schedule being such as to minimize the excess intotal heating value per unit volume of the mixture of base and peakshaving gases.

EDWIN X. SCHMIDT. CHARLES W. WARNER.

REFERENCES CITED UNITED STATES PATENTS Name Date Bucknam June 18, 1946Number

